(a) Field of the Invention
The invention relates generally to scaffolding systems and particularly to scaffolds with gear drives.
(b) Description of the Prior Art
Many scaffolds are known of the gear drive type and of the non-gear drive type. Scaffolding systems are made up of basic units from which high towers can be erected so that workers can do work on multi-story buildings. Typically, a pair of towers spaced-apart lengthwise are interconnected by cross braces to make a free-standing scaffolding unit. The units are aligned to make a continuous scaffolding for any desired length of wall. The towers can be vertically extended with tower inserts, typically 3 meters high, by adding them to a tower base unit. Any tower insert can be plugged into any base or any other insert. First, a pair of tower bases are erected upright on the ground level and interconnected by cross braces. Then, a number of tower inserts are added to reach full wall height.
A carriage, adapted to ride up on each tower, supports at least two plank platforms: the masons' platform which is typically adjustable from 25 cm to about 50 cm, and the material and laborers' platform, which is typically about 2 meters wide, and positioned above the masons' platform.
In a very common non-gear type scaffolding, each carriage has a winch that is operated by a laborer to raise the two-level platform as a wall is being built. The cable on the winch reaches up and is attached to a cable hook. A cable hook is built into the top of each tower insert. The carriage can be locked to the tower at any level to permit attaching the winch cable to a higher hook.
In a gear type scaffolding which I have previously developed, the carriage could move up but before it could move down, side panel braces had to be first removed. Also, after the scaffolding was fully erected to the height of the wall to be built, the movements of the carriage were limited to about 1 meter between such side panel braces. Accordingly, my prior scaffolding has not met with great commercial success.
The problems with known scaffolds will be better understood from the following.
The primary object of scaffolding is to provide safe working conditions for the laborers and masons. A secondary object is to achieve labor savings. Masons wish to go on the scaffolding when the wall is only about 1 meter above grade and also desired to be kept continuously at their most efficient working level until the wall is completed. Then they desired to move down as rapidly as possible on the scaffolding itself and not depend on a crane or lift.
A two-level platform is frequently raised to keep the masons working at their most efficient level. The material is stacked on the upper platform for easy reach by the masons who work from the lower platform.
The goal of good scaffolding design is that there be little interruption of production which means that the masons should not be required to move from one location to another, since each such move results in a loss of valuable time in reorganization before full production can be resumed. Thus, full production can be assured when there is no appreciable work interruption, while the platforms, material and workers are being moved to a higher level as the wall goes up.
For the same goal, the scaffolding should be erectable to full wall height before the masons go to work, and it should be capable of being easily extended while the wall is being built, using as a means for such extension the basic scaffolding units themselves without the aid of auxiliary machines.
A further consideration is the time it takes to set up, plank, and dismantle the scaffolding. While the wall is being erected and some material is used up, it may be desired that the workers and masons be allowed to move down to a lower level or to the grade level without having to first remove with auxiliary machines or a secondary scaffolding the cross braces and side braces under the planks.
In spite of such desirata, in known scaffolding including my previous scaffold, the removal of such braces from high scaffolding typically requires fork-lift trucks or cranes at considerable expense of money and of workers' time. Also, the erecting and dismantling of known scaffolds or the moving of their plank platforms to a lower level may require the setting up of an adjacent scaffolding, all of which consumes considerable time which is not productive as far as the wall construction is concerned.
A further objective is to be able to fabricate the scaffolding from common steel shapes using simple tools, such as welding tools which are widely available even in underdeveloped countries.
In sum, a careful study will indicate that the most serious problem facing known present scaffolding is the lack of flexibility in allowing the carriages on the towers to ride down with their platforms without having to first remove longitudinal braces, side braces, or panel braces which are used to tie pairs of towers or upright posts together where safety codes require continuous bracing.
It should be understood that when braces are removed under the platform, they may have to be replaced above the platform for maintaining the pair of towers in each scaffolding unit in fixed parallel relation. Such replacement is also very time consuming.
After experimenting for several years, I have now developed a gear-type scaffolding which is a great improvement over my previous scaffolding and eliminates therefrom the drawbacks above described.